[MPlayer-dev-eng] framerate conversion using framestep filter

[Patrick Cernko]

Hi list,

the appended patch against the current cvs enhances the framestep filter
to not only drop every nth frame, but to be able to set a "keep"-ratio,
a fraction, how many frames should (not) be droped. With this
enhancement, it is possible to do easy framerate conversion (only
dowmwards) by specifying a fraction of new and original framerate. For
example to convert NTSC material to PAL framerate, use:

... -vf framestep=2500:2997 ...

I have to use this for outputing NTSC material to my DVB-card. My card
of course also could decode NTSC material, by my TV set is unable to
present it in color (a really loosy one! :-( ). As I did not find a way
to use any other filter (mencoder's -ofps option is not usable when
preseting with mplayer), I patched the one, which already had most of
the stuff.

I only _added_ a new feature. I hope I did not overlook any case, so no
old features should be broken. The implementation uses int64_t-based
rationals to have highest precision. Although a int32_t-based
implementation would have been enough for easy cases like 3/4 or 15/16,
the above example of conversion from 29.97 to 25.0 requires
64Bit-precision to avoid computational overflows. Using the
rational-implementation, you get the most even drop distribution.

I hope this patch can make it in future versions of mplayer.

P.S.: @mplayer-dev-eng: As I have not subscribed your list, I would be
happy, if someone could send me a little note, if my patch made it into
cvs or was rejected.
-- 
Patrick Cernko | mailto:errror at errror.de | http://www.errror.de
Quote of the Week: "/vmlinuz does not exist.
                    Installing from scratch, eh?"
                   (Debian Kernel Installation)
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